The long-term goal of this study is to determine the extent to which protein synthesis can be supported and protein catabolism minimized in patients with trauma and/or sepsis by providing a minimal nitrogen intake as branched chain amino acids (BCAA) or their alpha-ketoanalogs. The objectives include determination of the effects of the BCAA in vivo on protein synthesis and degradation in the organism, the relationships of endocrine stimulation and substrate interaction, and the role of specific organs in the overall response of the organism. These studies will then be applied to a model of trauma/sepsis to determine the effect of the BCAA in this setting. The dog will be the experimental animal. The results of six day intravenous infusions of BCAA will be compared to equivalent infusions of nitrogen as mixed amino acid solution, calories as glucose, and alpha-ketoanalogs of the BCAA. Control influsion of water and electrolytes with starvation or regular diet will also be done. Biochemical monitoring will include nitrogen balance, concentration of circulating metabolites (amino acids, alpha-ketoanalogs, glucose, free fatty acids, ketones, lactate, pyruvate, glycerol), hormones (insulin and glucagon) and excretion of nitrogen and nitrogen components including amino acids. Comparison of results obtained with BCAA infusion to results from the various control infusions will allow identification of findings attributable to the BCAA infusion. Future studies of specific organ responses and the effect of sepsis will allow planning of further human studies, if appropriate.